Suspended file folders are well known. The most common types are formed from a folded cardboard folder that is attached at its upper edges to metal support bars. The support bars project from either side of the folder to form hooks engageable with suspension rails of a filing drawer.
While such folders have achieved considerable commercial success, they have a variety of disadvantages or weaknesses, including some or all of the following:                a. The support bars tend to be susceptible to being permanently bent or otherwise misshapen. Bent or misshapen bars alter the distance between the hooks, potentially causing the file folders to fall away from the support bar. The bars typically are of metal of a thickness that causes them to bend easily and permanently when loaded with weight from files.        b. The metal support bars glide poorly on the metal suspension rails. Thus in some versions, separate plastic inserts attached to the metal support bars are employed.        c. The folders are subject to frequent crumpling or ripping, particularly at a medial fold at a bottom end thereof when in use, which must bear both weight and impact from inserted files or papers, and also along the side edges.        d. At the top of the folder, the cardboard tends to detach as a result of general wear, poor quality glue, insufficient glue, or poor manufacturing techniques. This is observed both in designs where the cardboard has been folded over the support bars and attached to itself, and in designs where the metal bar and the cardboard are glued or otherwise fastened to each other.        e. Similarly, the metal bars tend to rip through the cardboard at the top of the folder due to handling, which causes the edges of the metal bar to cut through the cardboard.        f. Recycling of the folders is inefficient, since it requires separating the cardboard portion from the metal portion. The presence of adhesives may make recycling more difficult. In practice, the folders are therefore not often recycled, and instead they are discarded into the waste stream, which is obviously undesirable.        g. Manufacture of the folders is not as efficient as it would be if the step of securing the folder to the support bar could be avoided.        
Not all suspended file folders have all of the above problems, and indeed some designs have attempted to address some or all of these problems. U.S. Pat. No. 5,707,001 issued to Mark et al. on Jan. 13, 1998 teaches a suspended file folder made entirely from thermoplastic material, which makes it easy to manufacture and recycle. Two thermoplastic support bars are permanently fused one to each wall of the folder to provide strength and rigidity. The support bars are on the inside or outside of the folder. In order to enhance rigidity and strength, the support bars in Mark et al. are preferably provided with ribs.
Despite the improvements in Mark et al., it has been found that folders produced as taught therein, even with the enhancements, are not sufficiently durable in many situations where the weight of the folder contents is significant. Therefore, there is a need for improvement such as that provided by the present invention.